Optical fibers are used for transmitting electronic signals in high-speed data and communications systems. A standard optical fiber contains an inner light transmitting optical core. Surrounding each fiber is an outer protective casing. Optical fibers are utilized in the telecommunications industry, as well as other industries, as a preferred transmission medium because of their ability to carry large amounts of data at high speeds, over long distances.
Optical fibers are often terminated in connectors, so that they can be connected to other fibers or some other device. The “slot” that holds the fiber in position within the connector assembly is known as a ferrule. The precise positioning of the fiber in ferrules is necessary in order to consistently align one end of a fiber with the end of another fiber in a mating connector assembly, or with a device connected to the other end of the connector.
In the telecommunications industry, multiple fibers terminating at the back of a Fiber Distribution Frame (FDF) are connected via fibers within the frame to “ports” on the front side of the frame. These ports have rigid sleeves to hold the connectors in place, and apertures for the ferrules. In this way, the ports can be used to connect other optical fibers or electronic equipment plugged into the ports on the front of the frame to the fibers terminating on the back side of the frame.
If a port on the front side of an FDF is connected through the frame to the back side, and there is no equipment plugged into the port, there would be a fiber “end” exposed at the port. Further, if there is a “live” (powered) fiber connected to the back side of the FDF and associated with that port, the fiber end at the port would be emitting potentially dangerous light. The power level for some current systems with optical amplifiers is approaching 400 mW. For “next generation” systems it is expected to approach 1 W. At these power levels, the emissions could injure the eyes of a person looking at the port.
In order to avoid physical damage to the fiber end at an exposed port, and to avoid possible damage to the eyes of anyone looking at the ports, “dust covers” have been placed over the sleeves to protect both the fiber and the connectors from harmful dust or debris, as well as blocking any laser light emitted from the exposed fiber end. Covers could also be utilized in situations other than an FDF, such as to cover fiber connectors, or to cover fiber ferrules.
In the case of covers over sleeves on FDFs, these covers are routinely removed for long periods of time while service personnel are working on the front of the frame, looking at the ports. If a live optical fiber is connected at the back of the frame, and the port is not immediately tested when the cover is removed, the technician could be injured by the emitted light. Further, if the port is “live” for an extended period of time, the plastic cover could be damaged due to opto-thermal effects of the emitted light.
It would therefore be advantageous for service personnel to know whether a port is “live” before removing a cover from the port. It would also be advantageous to know if an installed cover is covering a live port, so that such a situation could be addressed before damage is done to the cover, or for other operational reasons. For instance, it may very well be a mistake that a “covered” port is live. Therefore, if there were an indication of this situation on a covered port, the problem could be resolved.
It would be further advantageous if the power level of light emitted from an optical fiber under a cover could be reduced while the cover is in place, in order to avoid damage to the cover.
It would be further advantageous if there was an indication that light within the spectrum used for communications was present under the cover, as opposed to extraneous light that would not be potentially harmful.